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Unit 2: The Continuation of Life

Unit 2: The Continuation of Life

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Unit 2: The Continuation of Life

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  1. Higher Human Biology Unit 2: The Continuation of Life Chapter 24: Regulating Mechanisms Mrs Smith Ch24 regulating Mechanisms

  2. Learning Intentions Success Criteria Mrs Smith Ch24 regulating Mechanisms To know how the heart rate is regulated. • Outline the principle of negative feedback • Explain how heart rate is controlled with reference to the role of hormonal and nervous system

  3. Human Internal Environment A human’s internal environment is the millions of body cells and the tissue fluid that bathes them. For a healthy body, all body parts must work together keeping the internal environment within tolerable limits. e.g. Human body must be maintained at 37°C to provide optimum conditions for enzyme controlled reactions The features of the internal environment are controlled by homeostasis…. Mrs Smith Ch24 regulating Mechanisms

  4. Homeostasis HOMEOSTASIS is the maintenance of the body’s internal environment within certain tolerable limits despite changes in the body’s external environment (or changes in the body’s rate of activity). Mrs Smith Ch24 regulating Mechanisms

  5. The value of Homeostasis Homeostasis is of survival value because it maintains the body’s internal environment at a relatively steady optimum state. If the body is exposed to extremely adverse conditions (e.g. freezing temperatures or absolutely no water) homeostasis will eventually break down, which in extreme cases can be fatal. Mrs Smith Ch24 regulating Mechanisms

  6. 8. Negative Feedback Control When a factor affecting the body’s internal environment deviates from its norm (or set-point) the body responds to correct the change. Image source: www.hw.ac.uk Mrs Smith Ch24 regulating Mechanisms

  7. 8. Negative Feedback Control Receptors detect change and send messages to effectors. • The change in the factor is detected by receptors. • These send out nerve or hormonal messages which are received by effectors. • The effectors then bring about certain responses which counteract the original deviation from the norm and return it to a set point. Image source: www.hw.ac.uk • This corrective homeostatic mechanism is called NEGATIVE FEEDBACK CONTROL. • It provides the stable environmental conditions needed by the body’s community of living cells to function efficiently and survive. Mrs Smith Ch24 regulating Mechanisms

  8. Sino-atrial node (SAN) = Pacemaker 9. Control of Heart Rate: Pacemaker Although the heartbeat is initiated by the pacemakertissue also known as a Sino-atrial node (SAN). However, heart rate is not set at a fixed pace. Heart rate can be altered by nervous and hormonal activity both of which exert control over rate (though not initiation) of heartbeat. Mrs Smith Ch24 regulating Mechanisms

  9. The Nervous System The nervous system is a network of specialised cells that communicate information about an individual’s surroundings and itself. It processes this information and causes reactions in other parts of the body. Mrs Smith Ch24 regulating Mechanisms Image source: www.drstandley.com

  10. The autonomic nervous system (ANS) controls involuntary responses to stimuli by the body. Autonomic nerves serve heart muscle smooth muscle Glands all internal organs. The ANS acts on these various effectors to maintain: homeostasiswithin the body (parasympathetic branch) response to stress – the "fight or flight" response (sympathetic branch) Control of Heart rate. The Autonomic Nervous System Mrs Smith Ch24 regulating Mechanisms

  11. Image source: www.biocomtech.com Parasympathetic v Sympathetic homeostasis response to stress Mrs Smith Ch24 regulating Mechanisms

  12. The vagus nerve is the longest nerve in the body, and one of the most important. It sends commands to, and takes information from many important organs including the heart and lungs. The Autonomic Nervous System: The Vagus Nerve People have two vagus nerves, one for each side, running roughly parallel from the medulla in the brain to the bowels. Mrs Smith Ch24 regulating Mechanisms

  13. Control of Heart Rate: • Autonomic nervous control The heart is part of the autonomic nervous system. It has branches of 2 parts of the autonomic nervous system. These 2 pathways have opposite effects on heart rate (are antagonistic). Heart rate is regulated by control centres within the medulla of the brain. Mrs Smith Ch24 regulating Mechanisms

  14. Control of Heart Rate: • Autonomic nervous control The sympathetic cardiac nerves carry nerve impulses from the cardio-accelerator centre of the brain to the heart. Causes an increase in heart rate Thecardio-inhibitorcentre sends nerve impulses via the parasympathetic vagus nerve. Causes a decrease in heart rate Mrs Smith Ch24 regulating Mechanisms Image source: http://courses.scholar.hw.ac.uk

  15. Two antagonistic pathways • The sympathetic and parasympathetic pathways are antagonistic to one another. i.e. They have an opposite effect on heart rate. • An increase in the number of nerve impulses conducted to the to the pacemaker by the sympathetic nerve causes an increase in heart rate. • An increase in the number of nerve impulses conducted to the to the pacemaker by the parasympathetic nerve causes a decrease in heart rate. Causes an increase in heart rate Causes a decrease in heart rate Mrs Smith Ch24 regulating Mechanisms

  16. Image source: www.rch.org.au B. Control of Heart Rate: Hormonal Control The adrenal glands produce the hormone adrenaline, which also affects heart rate. During exercise or stress…. Sympathetic nervous system causes the adrenal glands to release adrenaline At pacemaker: adrenaline causes an increase in the rate of cardiac impulses Increase in heart rate Mrs Smith Ch24 regulating Mechanisms

  17. Learning Intentions Success Criteria Mrs Smith Ch24 regulating Mechanisms To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems. • Analyse graphs showing distribution of blood to tissues at rest and during exercise • Calculate cardiac output under different conditions

  18. Vigorous exercise can cause huge changes of the body’s internal environment. The metabolic rate increases in the muscles that are working hard. need more oxygen need more glucose produce more CO2. The body adjusts to meet these demands and returns to normal a.s.a.p Experiments show (see Torrance p188) high levels of CO2 acts as the stimulus to trigger this. But severe lack of O2 can also cause this. Control of the Heart. C. Exercise Breathing rate & depthincreases to increase ventilation this promotes O2 uptake and CO2 removal View the Scholar animation: http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=92be7024-6e80-a2da-455b-e306b499a29a Mrs Smith Ch24 regulating Mechanisms

  19. Carbon dioxide as the stimulus Experiments show (see Torrance p188) high levels of CO2 acts as the stimulus to trigger an increase in breathing rate. The graph below shows the results! Only the ‘abnormal’ air type 2 is found to cause breathing rate to increase sharply. It is concluded that it is the high level of CO2 in the ‘abnormal air that acts as a stimulus triggering increased rate of breathing. Mrs Smith Ch24 regulating Mechanisms

  20. Carbon dioxide as the stimulus, Con’t • Further experiments show • Depth of breathing also increases in response to inhalation of air rich in CO2., • In a person under going strenuous exercise it is the increased level of CO2 in the bloodstream that acts as the main stimulus for bringing about an increase in rate and depth of breathing. Oxygen as a stimulus • It is worth noting that experiments also show that severe lack of oxygen will eventually also cause an increased rate and depth of breathing. Mrs Smith Ch24 regulating Mechanisms

  21. The effect of Exercise on the Respiratory System: Homeostatic control: Part 1 • Chemoreceptor's in the carotid arteries and aorta are sensitive to the concentrations of CO2 in the bloodstream. A rise in CO2 levels during vigorous exercise causes these sensory cells to send an increased number of nerve impulses to the respiratory control centre in the medulla. Mrs Smith Ch24 regulating Mechanisms

  22. The effect of Exercise on the Respiratory System: Homeostatic control: Part 2! • This region of the brain responds by sending a greater number of nerve impulses to the intercostal muscles and diaphragm. The subsequent increased activity of these structures brings about an increase in rate and depth of breathing. • Excess CO2 is removed and the internal environment is kept within tolerable limits. Mrs Smith Ch24 regulating Mechanisms

  23. High CO2 concentration SUMMARY: The effect of Exercise on the Respiratory System: Homeostatic control More nerve impulses sent to respiratory control centre in medulla Chemoreceptors in cartoid arteries & aorta detect CO2 concentration More nerve impulses sent to intercostal muscles and diaphragm An example of negative feedback control Breathing rate & depthincreasescausing a return to normal CO2 concentration Mrs Smith Ch24 regulating Mechanisms

  24. ml/min beats/min litres 1000 B. Effect of exercise on cardiovascular system Stroke volume = volume of blood expelled by each ventricle on contraction Heart rate (pulse) = number of cardiac cycles per min Cardiac output = volume of blood pumped out of a ventricle per min All of these increase with exercise and even more with strenuous exercise The stronger the contraction the higher the stroke volume Cardiac output Heart rate Stroke volume = X Mrs Smith Ch24 regulating Mechanisms To convert ml to litres

  25. Task!!! Mrs Smith Ch24 regulating Mechanisms

  26. Try this calculation! These figures actually show the effect of exercise on cardiac output for the average adult human! Mrs Smith Ch24 regulating Mechanisms

  27. Effect of exercise on cardiovascular system • The cardio-accelerator centre in the medulla sends impulses via the sympathetic nerves in the heart making it beat more often and powerfully. • This increase in both heart rate and stroke volume brings about the increase the total cardiac input needed to boost delivery of oxygenated blood to respiring tissues and to return deoxygenated blood to the lungs. • During very strenuous exercise, the cardiac output of an average person can increase by X5. This is mainly due to the increased heart rate. Mrs Smith Ch24 regulating Mechanisms

  28. Control of local distribution of blood • All parts of the body require an adequate supply of blood to function efficiently. But the demands by each part are not constant. • At rest the ‘vegetative functions’ (digestion, urine production etc.) are promoted. • When the body undergoes ‘strenuous activity’ much blood is diverted to the skeletal muscles (for extra O2 and glucose). Mrs Smith Ch24 regulating Mechanisms

  29. Increase in CO2 concentration Control of local distribution of blood During exercise… Chemoreceptors detect CO2 concentration Nerve impulses sent to cardio-accelerator centre in medulla An example of negative feedback control Nerve impulses sent to arterioles in working muscles causing arteriole wall to relax to increase blood flow Nerve impulses sent to arterioles in abdominal organs cause muscles in arteriole wall to contract to restrict blood flow Mrs Smith Ch24 regulating Mechanisms

  30. Distribution of blood to tissues during exercise During exercise blood flow to various parts of the body changes. Mrs Smith Ch24 regulating Mechanisms

  31. Task: Torrance-TYK pg192 Qu 1-3 Mrs Smith Ch24 regulating Mechanisms

  32. Learning Intentions Success Criteria Mrs Smith Ch24 regulating Mechanisms To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems. To know how blood sugar levels and body temperature are regulated. . • Explain how blood sugar level is controlled by the hormones insulin, glucagon and adrenalin. • Analyse glucose tolerance curves of normal and diabetic subjects

  33. DNA replication Regulation of Blood Glucose Concentration Blood sugar level must be kept within a certain range to provide the energy needed by cells for: • Synthesis of DNA, proteins and other complex molecules. • Active uptake of ions. • Muscle contraction. Cells are therefore constantly using up the blood sugar. To ensure a regular supply regardless of food consumed the body uses homeostasis! Mrs Smith Ch24 regulating Mechanisms Image source: library.tedankara.k12.tr

  34. Liver as a storehouse • About 100g of glucose is stored as GLYCOGEN in the liver. Glucose can be added or removed from this reservoir if stored carbohydrate depending on supply and demand. Mrs Smith Ch24 regulating Mechanisms

  35. Control of blood sugar: Insulin and glucagon • Insulin and glucagon are two hormones that control how much glucose (sugar) is in the blood • These hormones are made in the pancreas. • Your pancreas contains small groups of cells called the islets (or islands) of Langerhans. Mrs Smith Ch24 regulating Mechanisms

  36. Pancreas • When you eat a meal, the amount of sugar in your blood rises. The cells in your pancreas react by making more insulin. • When your blood sugar levels are low, the cells in your pancreas react by making more glucagon. Mrs Smith Ch24 regulating Mechanisms

  37. What does insulin do? • After digestion, glucose enters your bloodstream. • The Islets of Langerhans in the pancreas detects an increase in blood sugar level. • These cells produce the hormone insulin, which is then transported to the liver in the bloodstream. • Insulin activates an enzyme to catalyse the reaction glucose glycogen • This decreases the blood sugar level. • Glycogen, a long chain carbohydrate, is stored in the liver until it is needed e.g. when you are sleeping Mrs Smith Ch24 regulating Mechanisms

  38. What does glucagon do? • Glucagon stops your blood glucose level from dropping too low. • When you exercise, your body uses the glucose in your blood to power your muscles. Your pancreas senses that you're using up your glucose supply. • As your blood glucose level drops, your pancreas stops making insulin and your pancreas makes glucagon • Glucagon activates an enzyme in your liver which catalyses the following reaction Glycogen Glucose • These activities push up the amount of glucose in your blood. Mrs Smith Ch24 regulating Mechanisms

  39. Control of blood sugar Insulin Glucose Glycogen Glucagon Mrs Smith Ch24 regulating Mechanisms

  40. Task, can you place the boxes into the appropriate places in the table below! Mrs Smith Ch24 regulating Mechanisms

  41. Watch this Mrs Smith Ch24 regulating Mechanisms

  42. Adrenaline – Stress Response The adrenal glands produce the hormone adrenaline in an emergency when the body needs a quick supply of glucose (for ‘fight or flight’) Adrenaline is secreted by the adrenal gland and inhibits the secretion of insulin and promotes the breakdown of glycogen to glucose, overriding the normal homeostatic control. When the crisis is over the normal homeostatic control then returns the blood sugar level to its norm. Mrs Smith Ch24 regulating Mechanisms Image source: www.rch.org.au

  43. Alternative Homeostasis All factors controlled by homeostasis can be represented by a standard diagram. When a factor deviates from the norm and is returned to normal it often overshoots the mark, which triggers the reverse set of corrective mechanisms. So factors in a state of dynamic equilibrium are constantly wavering on either side of the norm. This is usually represented by 2 linked circuits. Mrs Smith Ch24 regulating Mechanisms

  44. Diabetes Diabetics suffering from Diabetes mellitus can not produce enough (if any) insulin which causes their blood sugar level to get too high. Because of this the kidneys can not reabsorb all of the glucose from the glomerular filtrate and so glucose is excreted in the urine. Diabetes used to be fatal but can now be treated with a carefully controlled diet or insulin injections. Mrs Smith Ch24 regulating Mechanisms Image source:

  45. Glucose Tolerance Test Glucose tolerance is the capacity of the blood to deal with the glucose we eat. It depends on the body’s ability to produce enough insulin. A known mass of glucose is drunk. Then the level of glucose in the blood is monitored & graphed to give a glucose tolerance curve. Mrs Smith Ch24 regulating Mechanisms

  46. Glucose Tolerance Curves Glucose level remains high Severe diabetic – insulin injections and carefully controlled diet needed Mild diabetic – condition controlled by diet Delayed response Glucose level returns to normal quickly Not diabetic - Insulin production normal Mrs Smith Ch24 regulating Mechanisms

  47. Watch this!!! Mrs Smith Ch24 regulating Mechanisms http://www.bbc.co.uk/learningzone/clips/the-effect-of-high-sugar-intake-on-blood-sugar-levels/5371.html

  48. Learning Intentions Success Criteria Mrs Smith Ch24 regulating Mechanisms To know how the heart rate is regulated and the effects of exercise on the cardiovascular and respiratory systems. To know how blood sugar levels and body temperature are regulated. • Explain how temperature is controlled with reference to; • The role of the hypothalamus • Nerve communication between the hypothalamus and effectors • Involuntary and voluntary responses • Changes in ability to control body temperature with age

  49. Control of Body Temperature • Core body temperature must remain at 37oC • Careful control of the blood supply to the skin can do this by reducing blood flow to the colder extremities in cool conditions. Mrs Smith Ch24 regulating Mechanisms

  50. Regulation of Body Temperature • Another example of homeostasis is the body’s regulation of body temperature. • The hypothalamus (the body’s temp-monitoring centre)monitors body temperature in two ways: It contains central thermoreceptors which are sensitive to temperature changes in the blood, allowing detection of the body’s core temperature. It acts as a thermostat by detecting nerve impulses from thermoreceptors in the skin (this conveys info about the surface temp of the body). Mrs Smith Ch24 regulating Mechanisms